What is the design factor for SMAW when specifying the effective throat, and how does it compare to SAW, FCAW-G, MCAW, and GMAW?

• A. SMAW 1.7; others 1.5
• B. SMAW 1.5; others 1.7
• C. SMAW 2.0; others 1.5
• D. SMAW 1.2; others 1.4

Answer: (A)

When sizing the fillet weld’s capacity, the effective throat is the portion of the weld that actually carries the shear load, and a design factor is applied to account for uncertainties in welding quality and service conditions. A higher design factor makes the required throat larger, meaning a more conservative weld is needed.

SMAW is assigned a higher design factor (1.7) because it is a manual process with more potential variability in bead shape, reinforcement, and the presence of slag or porosity. This greater variability requires a more conservative factor to ensure safety under less-than-perfect welds. The other processes listed—SAW, FCAW-G, MCAW, and GMAW—tend to produce more consistent and controlled welds, so a slightly lower design factor (1.5) is used for them. Therefore, the design factor for SMAW is 1.7, while the others are 1.5.